Shredders can be classed into two types, the stripe-cut shredders and cross-cut shredders, according to the machine cut style, the former comprises a set of blades used for cutting on revolving cut wheel to cut paper into strips, the latter comprises blades being provided with more than one hook-shaped edges and the edges are disposed helically around the revolving cut wheel to cut paper into strip longitudinally and cut paper into shatter of 5 mm×40 mm in latitudinal direction. Because the cut effect of latter is better than the that of garbage or the effect of keep security of destroying the contents on the paper, the cross-cut shredders has become the main flow of the market. Just because the cross-cut shredders cut paper more tinny, so the motor that provides the drive revolving cut wheel must more powerful than that of stripe-cut shredders. Besides because the blade used for cutting of stripe-cut shredders is provided with more than one hook-shaped edges, to avoid accidentally injure operator on the circumstance of the current is not break, so ISO have a regulation that the shredders must have safe activation switch, namely, cross-cut shredders act only on the condition that be set on the fixed position of garbage container provided with manufacture, on the contrary, if the shredders being removed from the garbage container the current will be broken.